This application relates in general to a method, apparatus, and article of manufacture for providing high-speed digital communications through a communications channel, and more particularly to a method, apparatus, and article of manufacture for providing a system and method for embedding a sub-channel in a block coded data stream.
Digital communications systems are continuously increasing the transfer rate at which data is transmitted between devices through a communications channel, for example, a backplane. One technique for increasing the data transfer rate is to encode the data prior to transmission. In this regard, there are a number of techniques for encoding data. Many of these techniques utilize different numbers of signals and modulation of symbols in order to increase the data transfer rate. One such method of modulating symbols is to use a multi-level pulse amplitude modulation (PAM-n) scheme that encodes a plurality of bits of data into or onto a single signal in which the symbols are represented as a set of signal levels between minimum and maximum signal levels. An n-level pulse amplitude modulation technique may result in a transmitted symbol rate that is (log (2)/log (n)) of the actual data transmission rate.
In certain data communications systems, adaptive controls are employed to facilitate proper decoding of the received signal to thereby recover the digital representation of the data bits being transmitted. These adaptive controls adjust or modify various operating parameters of transmitters and receivers of the data communications system. These parameters may be best determined using the specific topography and operating characters of the communications channel. In addition, these parameters tend to change over time and, as such, adaptively controlling the transmitters and receivers may enhance the operating performance of the communications system as that system changes over time.
When adaption is performed at the transmitter, there exists an inherent problem of communication. Any measure of performance can only be determined at the receiver, which is at the far end of the link. Therefore, information collected at the receiver must be returned back to the transmitter to adapt the output signal characteristics of the transmitter. The information sent from the receiver back to the transmitter to modify, change, optimize and/or enhance the output signal characteristics of the transmitter in accordance with the signal received by the receiver is termed a back channel.